Difference between Mucus and Phlegm

What is Mucus?

Mucus is a normal, slippery and stringy fluid substance produced by many lining tissues in the body. It is essential for body function and acts as a protective and moisturizing layer to keep critical organs from drying out. Mucus also acts as a trap for irritants like dust, smoke, or bacteria. It contains antibodies and bacteria-killing enzymes to help fight off infections.

The body produces a lot of mucus about 1 to 1.5 liters per day. We don’t tend to notice mucus at all unless its production is increased or the quality of mucus has changed, as may happen with different illnesses and conditions.

What is Phlegm?

Phlegm is a liquid secreted by the mucous membranes of mammals. Its definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing (sputum). Phlegm is in essence a water-based gel consisting of glycoproteins, immunoglobulins, lipids and other substances. Its composition varies depending on climate, genetics, and state of the immune system.